International Journal of Application or Innovation in Engineering & Management (IJAIEM)
Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
Volume 2, Issue 5, May 2013
ISSN 2319 - 4847
The Effect of Particles as Additives on
Water Absorption for Epoxy Resin
Asmaashawky kalil
University of Baghdad, College of science,
Physics department,Jadiriya,
Baghdad, IRAQ
ABSTRACT
Diffusivity behavior and diffusion coefficient was investigated in this paper for epoxy composite reinforced with metal(Al ,Cu ,
Fe) and metal oxide (Al2O3,Fe2O3,and CuO2 (with different weight percentage (5,10,15,20,and25%). The samples were
immersed in water equal time for two months at constant temperature (room temperature 18C). The result show that the
relative mass gain increased with increasing the immersion time till they tend saturation moisture mass (M∞) after that the
relative mass gain decreased. Also the results show that the immersed samples in water filled with metals has maximum
diffusion coefficient (4.73E-07cm2/sec) for EP/Al while the samples filled with metal oxides has maximum diffusion
coefficient (3.41E-07cm2/sec) for EP/Fe2O.
Keywords: Particulate composite, water absorption
1. Intoduction:
EPOXY resin composites are widely used for the insulation of power transformers, switchgear, rotating machines, etc.
The sensitivity of epoxy composites to humidity is a serious matter of concern because absorption of water may cause
significant and possibly irreversible changes to the material [1]. Epoxy resins can absorb up to a few weight percent of
water in a humid environment, leading to an overall degradation of the dielectric properties. Such a situation might be
further exacerbated by inorganic fillers, which are often used to improve their mechanical and thermal properties and to
reduce their cost[2].
Polymeric matrix composites differ from other materials in the sense that low- molecular weight substances such as
watermay easily migrate even at room temperature generating variation of the material's structure, morphology, and
composition [3]. In many cases, it could lead to an irreversible degradation of the material in the so- called humid
aging that includes both chemical aging and physical aging. The epoxy matrix show moisture sensitivity due to
Interactions between some polar groups of the macromolecule and the water molecules, which leads to a reduction of
both glass transition (Tg) and mechanical properties. This sensitivity increases with the increasing degree of crosslinking and also with the polarity concentration of the molecular groups [4]. The physical phenomena that
simultaneously occur are dissolution, diffusion, swelling, and relaxation, together with deformation and stress build up
in the matrix
The relative mass gain can be obtained by:
M%= mass of wet sample – mass of dry sample x 100/Mass of dry sample
….(1)
And the diffusion coefficient can be obtained by:
D =π (kb/4M∞) 2 …
……………………………………………….………. (2)
where:
D: diffusion coefficient (mm2/day) , b: thickness of the sample(mm)., M∞: saturation moisture mass (gm).and K: the
slop of the curve between mass gain and immersion time [5].
his diffusivity D, defined as the amount of liquid passing per second through a unit area under the influence of a unit
gradient of concentration is still a function of the temperature T given by an Arrhenius expression:
D = Do exp (-HD/RT)
………(3)
where: HD: activation energy for diffusion. R: gas constant.
The diffusion time (tD) defined as the duration of the transient and can be calculated as:[6]
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
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Volume 2, Issue 5, May 2013
ISSN 2319 - 4847
tD = π b2/16 D
……..(4)
Moisture diffusion in polymeric composites has shown to be governed by three different mechanisms [7, 8]. The first
involves of diffusion of water molecules inside the micro gaps between polymer chains. The second involves capillary
transport into the gaps and flaws at the interfaces between fiber and the matrix. This is a result of poor wetting and
impregnation during the initial manufacturing stage. The third involves transport of micro cracks in the matrix arising
from the swelling of fibers (particularly in the case of natural fiber composites). Generally, based on these mechanisms,
diffusion behavior of polymeric composites can further be classified according to the relative mobility of the penetrate
and of the polymer segments, which is related to either Fickian, non-Fickian or anomalous[9], A. Abd Alameer study
electrical conductivity behavior of Cu-powder reinforced epoxy composite material in different solutions (distilled
water, tap water &3.5%NaCl) with different a weight fraction [10], W. S. Chow* study Water absorption of epoxy/glass
fiber/organo-montmorillonite nanocomposites[1]
Although the diffusion coefficient is not a direct measure of mechanical deterioration, it is a relative measure of the rate
at which the composite absorb water and the mechanical properties deteriorate.
2. Materials and testing procedure
The material used to prepare the test samples were epoxy resin (EPI0 Conbextra) with the hardener aliphatic amine (Hy
956) in ratio 3:1 for curing. Three type of metal (aluminum, iron, copper) and metal oxide (of purity 99.5%) used as
fillers in this work. A weight amount of epoxy was mixed in (5%, 10%, 15%,20% and 25%) percentage. Table (1)
summarizes the materials and some of their properties.
A hand lay up method was used to lubricate all the specimens in this work and many testes showed that the ratio of
hardener to epoxy, which will be used in this study, is approximately [3:1], to prepare the composite sheets, which are
cut later to get the samples(1*1)cm according to ASTM_D570 .The additives powder was added to the epoxy ,stirred
for 5 minutes to be well mixed and for more diffusion the mixture was put in the oven at 500 C for 15 minute. The
mixture was then left for 24 hours for curing.
All prepared sheets were checked by optical microscopic to see the good dispersion of the particles distribution.
The dray samples were weight and then immersed in water for (8 weeks), at the first week the samples weighted daily
then every two weeks with sensitive (starorius) by W-Germany, It was proven to be a sufficient time for reaching the
steady state.
Table 1: some of properties of the used material
Material
Sample
Density
3
(g/cm )
Epoxy
EP
1.2
Aluminum
Al
2.7
Particle size
(µm)
10.2
Iron
Fe
7.3
15.01
Copper
Cu
8.9
12.42
ALUMINUM
AL2O3
3.96
9.76
CU2O
6
15.2
OXIDE
CAPPER
OXIDE
Water diffusion in epoxy materials was measured at room temperature (298K). Water sorption in the resins as a
function of the square root of processing time (hours) was monitored by this gravimetric method. The specimens were
periodically removed from the water, wiped down, and quickly weighed on the microbalance until the percent weight
did not change.
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3. Results and discussion
To determine the diffusion coefficient, the specimens were soaked in water at room temperature and the weight changes
were monitored as a function of time. The percentage weight change M was calculated by equation (1).
The plotted curves of figs . (1) , (2) ,and (3) show the variation of water gain M against the square root of the
immersion time  t for neat epoxy resin and its different metal, and metal oxide composites. It is seen that the water
uptake increased linearly with increasing of the square root of immersion time, then gradually slow until an
equilibrium plateau is reached. This is similar to the prediction of Fickian behavior. The plateau is defined as the
apparent maximum water content M[1].
Water diffusion of neat epoxy and its composites were calculated from the relationship between weight gain M and
diffusivity during initial water uptake for Fickian diffusion which is given by equation (2) .
Diffusion coefficients values were evaluated and listed in Table (1) the results reveal that the diffusion coefficients of
resin composites are less than that of net epoxy.
Table (2) also shows that the diffusion coefficient of specimens of epoxy / metal oxide composites are less than epoxy
resin and epoxy / metal composites , because of reaction between epoxy and (H2O) through the interface making a
separation between the epoxy and particles [11].
Water diffusion gives an indication of the affinity of the polymer to water and the degradation of the resin caused by
water. The diffusion rate depends on the surface condition of the resin, i.e., airtight or ventilated, and the dispersion of
micro voids in the resin. If the initial diffusion rate is quick, this suggests that the surface of the resin is porous, and the
micro voids in the resin are connected [9].
Figure 1: Weight gain Mt% as a function of square root immersion time of Epoxy resin.
Figure 2: Weight gain Mt% as a function of square root immersion time
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of Epoxy and EP/Metal composites
Figure 3: Weight gain Mt% as a function of square root v.s immersion
time of EP/Metal Oxide composites
Table 1: Diffusion coefficient of neat epoxy resin and metal/epoxy composite
Composites
Diffusion coefficient (cm2/sec)
Wt%
5%
10%
Al
4.73E-07
1.78E-07
Cu
2.39E-07
2.26E-07
Fe
4.73E-07
1.78E-07
15%
2.19E-07
2.08E-07
2.19E-07
20%
2.22E-07
2.53E-07
2.22E-07
25%
2.62E-07
1.75E-07
2.62E-07
Epoxy resin
5.81E-07
Table 2: Diffusion coefficient of neat epoxy resin and metal oxide/epoxy composite
Wt%
Diffusion coefficient (cm2/sec)
Composite
Al2O3
5%
10%
3.08E-07
2.73E-07
3.57E-07
1.83E-07
1.90E-07
1.85E-07
15%
1.81E-07
1.48E-07
2.13E-07
20%
1.38E-07
1.98E-07
1.19E-07
25%
2.19E-07
3.41E-07
1.57E-07
Epoxy resin
5.81E-07
Volume 2, Issue 5, May 2013
Fe2O3
Cu2O
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The water absorption behavior of polymer-filled particles composites at a humid environmental condition is determined
by many factors, such as processing techniques, polymer matrix and filler characteristics, composition of the
composites, and so on [12].There are two situations for water sorption in composites filled with inorganic fillers:
• One is when there is a good interfacial adhesion established between the matrix and the particles. This may result in a
higher density composite and less free volume around the particles. If there is a higher concentration of inorganic
particles, the denser interface zones between particles and matrix means that less water can be contained in this region
[12].
• Conversely, some bonds between epoxies and some filler (such as ceramic and aluminum) are thermodynamically
unstable or not strong enough in the presence of water molecules. The thermodynamic work in the interfaces between
fillers and matrix could become negative in the presence of water from the positive value when dried. For example, the
thermodynamic work for the epoxy-ferric oxide interface changes from +291 to -255 mJ/m2 when there is an absorbed
layer of water at the interface [12,13]. This change from a positive to negative work of adhesion provides a driving
force for the displacement of adhesive on the interfaces between particles and epoxy matrix by water [2]. It is therefore
to be expected that the interfaces between the inorganic fillers and matrix might be de bonded in the presence of water.
At The higher concentration of inorganic particles, the more broken bonds, and therefore the water can be contained in
this interfacial region. The generally accepted mechanism for solution sorption in polymers is an activated sorptiondiffusion process.The molecules first dissolve into the polymer surface and then diffuse through the bulk of the polymer
by a series of activated steps. The amount of absorbed water depends on the temperature, the structure and the
morphology of the polymer [13]. It is clear from the measurements that the epoxy in the micro-filled system absorbs
about the same amount of water as the pure epoxy for a given humidity and that, for the micro-filled system, virtually
all the water is absorbed by the epoxy, because water has polar dipole when these molecule were diffused into Polymer,
the polar dipole will act as electrostatic force between polymer back bone chains, so that the polymers become more
strength [15, 17, 18]
Diffusion is the net movement of matter down a concentration gradient due to the random movement of individual
particles. The process is dependent on the imposed boundary condition [11]. When a dry specimen is put in a humid
environment, then, after some time, a steady state is obtained in which water diffusing through the plane per unit time
is zero. Within the plane, the concentration gradient is not zero. However, once a steady state is established, the
concentration at any location does not change with time. This defines a steady state, and Fick’s First Law is most useful
in dealing with this situation [14]
4. Conclusions
a) The results reveal that the diffusion coefficients of resin composites are less than that of net epoxy
b) Also the results shows that the diffusion coefficient of specimens of epoxy / metal oxide composites are lessthan
epoxy resin and epoxy / metal composites
c) The results show that the immersed samples in water filled with metals has maximum diffusion coefficient (4.73E07cm2/sec) for EP/Al
d) the samples filled with metal oxides has maximum diffusion coefficient (3.41E-07cm2/sec) for EP/Fe2O3
5. Refrences
[1.] W.S.Chow "Water absorption of epoxy/glass fiber / organo- montmorillnite nanocomposites" expresss Polymer
Letters Vol.1,No.2 (2007) 104-108.
[2.] 2-R.Padmd Suvrna,K.Ragha "Asiple technique for a.c conductivity measurement ", Vol.25, No.7 pp.227-233
(2000)
[3.] 3-R.T.Fuller,R.E.Fornes,and S.D.Memory"NMR study of water absorped by epoxy resin " J.apple.polym.Sci.23
pp1871-1874 (1979)
[4.] 4-A.Apicella,RTessiri,andC.Decalataldis" sorption mode of water in glassy epoxies"J.memb.Sci.18: pp.211-215
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[5.] 5-Abot, J.L., yasmin, A. Jacobsen, A.J. and Daniel, I.M, "In- plane mechanical thermal and visco elastic properties
of a satin fabric carbon/ epoxy composite", compos. Sci. Tech. 64: (2004) pp (263-268).
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[7.] 7- G.C.papanicolaou ,A.G.Xepapadaki,D.Zarouchas"Effect of water uptake on the creep behavior of glass-epoxy
composite"13th Eurepan Conference on Composite Materials June 2-5 ,2008 stockholm.Sweden
[8.] 8- Zainab Raheem"water absorption of denture base polymer reinforced with glass fibers in chopped and woven
form" CSAASC English Ver.,Vol.4 College of Scientific Conference, 2009
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Web Site: www.ijaiem.org Email: editor@ijaiem.org, editorijaiem@gmail.com
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[9.] 9- H.I.Jafa, S.I.Husaen,and E.A.Al-Ajaj "Effect of water absorption on some electrical and dielectrical properties of
epoxy resin
reinforced with
chopped carbon
fibers "Journal of Al-Nahrain University
Vol.14,(4),December,2011,pp.87-94.
[10.] 10- Nirvana A.Abd Alameer (Study the effect of electrical conductivity of Cu powder reinforced epoxy composite
materials " Eng.& Technology.Vol.30,No.2,2012
[11.] 11- Mayers, M.E. and Abu- Isq, I.A.( 1986), J. Appl. Polym. Sci. 32 pp. (2515-2520).
[12.] 12- Alan J.Lasser and L.H.Sperling ,Int to Physical Polymer Sci., , 2006 , Jhon Wiley and Sons Inc.
[13.] 13- James E.Mark, Physical properties of polymer handbook , 2nd edition Springer , 2007.
[14.] 14-Hin D,Annette M.,Advanced materials and structures and their fabrication processes ,Third edition Narvick
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[16.] [16] Negele O, Funke W. Internal stress and wet adhesion of organic coatings. Prog Org Coat 1996;28:285–9.
[17.] [17] Bower DI. An introduction to polymer physics. Cambridge: Cambridge University Press; 2002.
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[19.] 18- Markus P.K. Turunen a,*, Pekka Marjam€aki a, Matti Paajanen b, Jouko Lahtinen b, Jorma K. Kivilahti
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